98 SOHC - Hesitation driving me crazy! Help needed...

[2000StreetRod]

FPR & pressure

I read this entire thread from the beginning and noted that you have not replaced your fuel pressure regulator (FPR) nor have you ever actually tested your fuel pressure. I believe that you have the return fuel system with a FPR on the fuel rail and a return to the fuel tank. Here in the states the 1999 and later models have the FPR in the fuel tank and the system is returnless.

Even though you have replaced your fuel pump and fuel filter there is still the possibility that your FPR is defective. When you accelerate moderately the vacuum decreases temporarily and the FPR should increase the fuel pressure accordingly. If the vacuum diaphragm is defective the pressure may not be increasing and your engine may be starving for fuel. You stated that it is difficult for you to obtain a Schrader valve compatible gauge. I believe that you can unscrew the valve and clamp a hose over the test port. It's actually more accurate that way and many members prefer the method. Once again I strongly suggest that you test your fuel pressure with emphasis on acceleration (low vacuum) values. See my Fuel pressure test procedure

 

[foxy]

Hi Gilly, Mate you have the same problem I have ,but mine is a lesser degree .I'm about to replace my fuel pump with a high performance one hoping it will go some way to fixing it BUT .I have changed my filters and I have a fuel pressure gauge on the rail and it tells me there is definitely something wrong with my pressures as they are all over the place .At ignition it settles at 45 psi and at start up jumps to 100 psi and then flickers between 48 psi and 100 psi I'm sure the gauge is okay as it is new even though that's no guarantee. At load it will dip to 45psi and then up to 100 psi .I'm having my fuel system checked out just to eliminate the gauge but I feel it may be the fuel regulator which I understand is on the end of the LHS rail at the back . You also have to be aware ours are right hand drive and the placement of things doesn't always match ours as to the US . James from Henson is a great guy I bought a SF3 from him and 3 programs and they are excellent . Gilly I have the 99 US manuals not the Aussie ones so I'm not sure if my 9/99 sohc is a return less one .I have one pipe out of the tank and there is another one which is connected directly to the tank whick may well be the return . I'm not sure of the cost of a regulator out here as I haven't got that far as yet .Cheers Foxy

 

[gilly]

Good suggestions, Yes - you're right, I need to look into the fuel pressure regulator side of things. Yes I do have the FPR on the fuel rail - easily accessible. Some tests I have done with this are check for fuel smell from the vacuum side - no smell, and I also disconnected the vac line (and taped over the line) so that the FPR would effectively be giving the engine full fuel pressure and took it for a drive like that and the hesitation was still obvious at the same rev range.

Maybe it's not opening up as much as it needs to though?

Foxy - what gauge are you using on your fuel rail and where did you get it from?

 

[foxy]

Hi Mate, I got my gauges from the US, they are GLOWSHIFT . I couldn't find a fitting for the Shrader valve at the fuel rail so I went to my local tire guy at Bridgestone and bought an extension . to fit it and the bought a 1/8NPT socket to suit the gauge .I cut the socket end off the extension and brazed the 1/8 npt socket to it so I could mount my sender unit onto the end of the fuel pipe ps don't forget to remove the valve and the rubber washer from the extension before you braze it .The Glow shift gauges are great as you can change colours and also the are above average gauges .Try Google you should find them . I also bought a trans temp engine temp engine oil pressure and fuel pressure as the gauges in the Explorer only tell you after the event whereas proper gauges can tell you before hand ,If I hadn't had the fuel pressure one I would not be aware that something is possibly wrong with my fuel system.Hope this can help Cheers Foxy

 

[foxy]

I forgot to tell you .The valve in the fuel line is down pretty deep in the pipe you will need a long valve remover tool to reach it be careful when removing the valve though NO ignition Cheers Foxy

 

[2000StreetRod]

closed to open loop transition

I've been looking at the closed to open loop transition in the datalog that you sent me. I think that the knock sensor can safely be eliminated as a possible source of your problem. I wish that mine behaved like yours!

I noticed that your timing immediately begins to retard as soon as the throttle is opened and the MAF sensor value increases. I wish that you had recorded the computed load so I could tell how fast that is changing relative to the other parameters. Anyway, from the rest of the datalog it appears that the timing is functioning normally as long as there is light load on the engine. It also appears that your TPS output is reliable although I can't tell the difference between you moving the accelerator and the TPS changing value on its own. As your throttle approaches WOT your short term fuel trims change to rich and stay constant.

It appears that your engine is unable to support the load increase and the PCM tries to compensate by retarding the timing. I believe that it is a general engine weakness as opposed to a cylinder specific weakness because there are no misfires detected and reported by the PCM. The general engine weakness could be due to improper fuel mixture (way rich or way lean) or feeble ignition. It seems unlikely that your ignition would be adequate at 5000 rpm but inadequate when accelerating at 2600 rpm.

I still suspect that you have a fuel supply problem. When you rapidly accelerate the engine vacuum immediately changes from 19 inches to around 5 inches. Your fuel pressure regulator (FPR) alters the fuel pressure according to vacuum with the highest fuel pressure occuring with no vacuum. When you "mash" the throttle the FPR rapidly increases the fuel pressure giving the injectors a boost to keep the engine from stumbling. That is one reason that I prefer the return fuel system over the returnless one that I have. My returnless system is dependent upon the PCM to provide the injector boost and according to my A/F ratio meter the PCM's performance in this regard is mediocre. I don't think your FPR/fuel filter/fuel pump is up to par. But this is all speculation on my part. Only testing with a fuel pressure gauge will determine if I am correct. You may have to connect the gauge so that you can read it while driving your vehicle under load.

 

[gilly]

Thanks for the tips Foxy.

2000StreetRod - I think you could be right about the fuel system. The TPS is working fine - I did lift off at times to stop it kicking down a gear, I really was aiming to hold it in this 'hesitation' state.

I emailed that file to James as well - here's his feedback: "One thing I notice is when the spark goes retarded the battery voltage drops .3 volts. We both know that this isn’t enough to hurt anything but obviously there is a huge power draw when this occurs. Such a strange anomaly, I would check coil wiring, crank and cam position sensors for damage. The crank and cam sensors are only 5V sensors but could cause major issues."

Both of those sensors have been swapped over (but using 2nd hand sensors)

 

[gilly]

Ok well in the last few days I've been removing grounding wires, cleaning and refitting - body to chassis both sides, ecu and the centrally located one on the firewall just above the intake manifold.. I've disabled the dual battery isolator, disabled my trailer electric brake controller, cleaned the terminals on the battery, the alternator, the master fuse between the battery and the alternator on the power control box, Removed and refitted the loom to the ecu and the other major loom connection just in front of the ECU.

I picked up a 2nd hand alternator for $50 to see if that's been a contributing factor, installed that today and I've picked up 0.5v overall at least, so that's been worthwhile and I'll get original one rebuilt and back on in a few months.

Also just picked up a Fuel Pressure Test Gauge on eBay that should hook up to my rail easily. It looked similar to the one in 2000StreetRod's Fuel pressure test procedure thread so I went for it. Not easy to come by these at a low price in Australia, the only other one I've seen here is Snap-On and $400+ so I thought this was a bargain at $40 and went for it. I'm keen to see the results!

Also - the interference/spikes issue with the datalogger, I've got a spare ECU sitting here so I'm thinking of just swapping them over to see if that solves the issues too. I'll need to get the PATS (Passive Anti-Theft System) disabled to use it though - I've emailed James @ Henson Performance about this, I've read that he's done it before.

I feel I'm getting closer to the answer!

 

[2000StreetRod]

Making progress!

You've made good progress toward increasing your supply voltage and 13.6 volts is probably adequate but still low compared to mine. Has the spiking been reduced any?

Have you stored a copy of your (in the vehicle) stock strategy tune on your X3? If not, I suggest that you do.

Are you sure it is necessary to disable PATS before you can use the spare PCM? PATS has a lot of built in capabilities and communicates with the PCM. I would just swap out the PCM and try it if you haven't already. Your X3 will support up to 5 different VINs so it should be able to store a copy of each strategy tune for both PCMs. It just can't store more than 3 custom tunes at a time.

The fuel pressure test kit you ordered looks very similar to mine. Since the description says it supports Ford it should have the Schrader valve compatible fitting.

 

[gilly]

I've stored the stock tune both on the X3 and backed it up on the laptop. I tried the spare PCM but it wouldn't start the truck - turns over the starter and the anti theft light comes on the dash, that's all.

Got a PATS disabled tune from James @ Henson Performance today and uploaded it to the spare PCM. Truck fired up and ran PERFECTLY - NO HESITATION! I'm still seeing spikes in the Datalog - I can live with that.

Here's the bad news: It's now throwing DTC's like crazy.

I'm getting the following:
P0453 - Evaporative Emission System Sensor/Switch High Input
P1451 - Evaporative Emission System Vent Control CK T
P0141 - O2 Heater (HTR-11) CK T (B1,S1)
P0161 - O2 Heater (HTR-22) CK T (B2,S2)
P0325 - Knock S1 CK T (B1)

 

[2000StreetRod]

Different firmware?

The tune that James sent you was probably for the original PCM. One of the first things he does is to confirm the firmware loaded into your PCM. The spare PCM may have different firmware for an earlier or later version of the vehicle. You don't want to be introducing a lot of variables into what James is doing. If James' tune is for the stock PCM, I would put it back in and load James' tune into it. Then see what happens with the stock PCM and the PATS disabled. If you recall, I thought that your PATS might be interfering with your OBD-II bus. James is the expert so just provide him with the results and let him decide on the best approach - which PCM to use.

 

[2000StreetRod]

fuel pump electrical test

I've added a new procedure called Fuel Pump Electrical Procedure
I suggest that you perform steps #6 and #7 to test the fuel pump electrical path to ground.

Somewhere on this forum a member posted the typical current draw for the fuel pump that I'll try and find. I seem to recall it was only a few amps. I believe the member pulled the fuel pump relay and then used his high current meter to connect the path instead of the relay. It was a very helpful post to easily determine if the pump was behaving normally.

 

[2000StreetRod]

> 3 amps on a 1992

I found the post by Opera House. He was troubleshooting a fuel pump problem on his 92 XLT and ran a wire from the battery to the pump side of the fuel pump relay. He measured the current thru the wire and found that it had to be greater than 3 amps for the pump to run. The 92 model has a return fuel system as does your 98.

Here's another post by Opera House:

"If you have an electrical meter, you can pull the fuel pump fuse and measure current at that location. Should be over 3.5A. Below 2.5A the engine will start to stall. Pump current gives a good overall indication of the fuel system. There could be some electrical resistance doping pump voltage like a pump relay with burned contacts."

 

[gilly]

Thanks for the replies 2000StreetRod - I'll definitely be trying that too soon.

The fuel pressure tester arrived today to here's the results from that.

I had a few issues with the gauge, it has valves at every extension, and one of the mid-way valves stuck causing inaccurate readings, so I ended up removing the valves from the fittings and it was far more responsive.

Findings:
30psi @ idle
40psi @ idle no vacuum
30psi @3000 (increases to 40 then settles back at 30psi.)

Under load - I left the hood popped just catched and ran the gauge out to the side of the bonnet and duct taped it there - worked perfectly! Went for a quick drive around the block and very happy with the results.
Even the slightest bit of acceleration and it's up to 40psi, under full load, 2nd gear takeoff uphill, remained at 40psi all the way until I backed off - then straight to 30psi. My haynes manual puts this well in standard spec, so I think we can safely count the fuel side of things out. Engine off it sat at around 35psi and didn't move.

So at this stage, I am leaning towards an electrical problem and also have my eye on the noise suppression capacitor that's bolted to the coilpack. After datalogging with this connected and disconnected I can't find any difference in noise at all, and seeing as though I'm experiencing a lot of spikes in the datalog, I'm hoping that this capacitor is the root of the problem. It's next on my hit list anyway! It's the power draw under load that has me confused - I'm not sure that a little capacitor could be capable of this? We'll soon find out.

 

[2000StreetRod]

Fuel pressure & vacuum eliminated

I agree that you can now eliminate fuel pressure/delivery as the source of your hesitation. You've also verified that your vacuum is responding normally to engine load.

It's not likely that a bad radio noise suppression capacitor is causing your spikes. The spikes do not appear to be correlated with engine speed or anything else in your datalog.

The radio noise suppression capacitor can't be the cause of your low voltage. If shorted it would either burn out or blow a fuse at the current draw required to drop your supply voltage from 14 to 13.5 volts. I would pull fuses to see if I could isolate to the drain on the supply. Electric motors (blower, windows, seats, wipers), heaters (seats, rear window), solenoids (door locks, rear hatch), amplifiers and lights are good candidates. Why did you add a second battery?

Did you switch back to the stock PCM or stay with the spare PCM?

 

[gilly]

I stayed with the original PCM as the spare one was throwing too many DTC's - something wasn't right.

The second battery is to occasionally power fridges etc while camping. I don't keep the second (deep cycle) battery in the truck anyway. Only have it fitted when needed so it's not a possible cause of any problems this time.

 

[gilly]

Ok still working on this problem almost daily.

Here's where I'm at today. Going by the datalogs I'm sure that something is throwing the spark out wildly and that's what's causing the hesitation. So thinking about what effects the spark, and which sensors I haven't swapped out yet, today I headed for the coolant temp sensor.

I unplugged the two looms near the thermostat and datalogged the truck. It immediately threw a CEL as expected and the dash gauge didn't work - perfect I thought all was disconnected. However it still logged an accurate temperature?? How is this possible? Is there another sensor somewhere I'm not seeing? It made no difference with these two disconnected, but as it still logged a temp I'm guessing there's a sensor elsewhere? Any ideas?

cheers
Gilly

 

[Mirge]

Almost 3 months working on this... yikes

 

[2000StreetRod]

ECT sensor

. . .
I unplugged the two looms near the thermostat and datalogged the truck. It immediately threw a CEL as expected and the dash gauge didn't work - perfect I thought all was disconnected. However it still logged an accurate temperature?? How is this possible? Is there another sensor somewhere I'm not seeing? It made no difference with these two disconnected, but as it still logged a temp I'm guessing there's a sensor elsewhere? Any ideas?
cheers
Gilly

According to everything I've read the following are the only temperature related sensors:

Intake Air Temperature (IAT) sensor reports to PCM
Engine Coolant Temperature (ECT) sensor reports to PCM
Engine Coolant sender drives temperature gauge on instrument cluster
Transmission temperature sensor reports to PCM

Disconnecting the Engine Coolant sender resulted in your dash gauge not working but would go undetected by the PCM.

Disconnecting the ECT sensor should have resulted in one or more of the following DTCs:
P0115 Engine Coolant Temperature Circuit Malfunction
P0116 Engine Coolant Temperature Circuit Range/Performance Problem
P0117 Engine Coolant Temperature Circuit Low Input
P0118 Engine Coolant Temperature Circuit High Input
P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P0126 Insufficient Coolant Temperature for Stable Operation

Are you sure that you actually disconnected the ECT sensor? I believe it's the sensor under the intake manifold and closest to the left upper chain tensioner. It should have two wires connected to it. A LG/RD that goes to the PCM and a GY/RD that connects with the other sensors (TPS, DPFE, CMP, IAT) common return to the PCM.

If so, then either you are datalogging the wrong parameter or the PCM is using some algorithm to estimate the engine coolant temperature. I briefly reviewed the last datalog you sent me and the engine coolant temperature seemed normal except for an infrequent spike.

 

[gilly]

Hi Dale,

Yes disconnecting both looms near the thermostat resulted in the dash gauge not working and the CEL coming on, throwing the code P0118 - Engine Coolant Temperature Circuit High Input

I'm guessing that the PCM is using an algorithm to estimate the coolant temp - if this is the case it's quite accurate!? It even increased a few degrees while datalogging. Interesting. I'm now going to try disconnecting one sensor at a time and datalogging to see if that has an effect on the spikes I'm seeing. If one sensor has a bad ground, maybe this will help locate it.

cheers
gilly